was found that under the influence of high waves the transport of sediment 

 is rapid and that useful data can be obtained within the time available 

 before decay of the radionuclide seriously reduces the radiation available 

 for detection.) 



133 



Because Xe is biologically inert and has a half -life of 5-27 d, it met 

 most of our criteria for sand-tracing experiments. However, the low-energy 

 (80-keV) gamma radiation required that the detector system have a high de- 

 gree of sensitivity and imposed the limitation that only tagged sand moving 

 at or near the surface of a sand column could be detected. On the other 

 hand, the use of low-energy gamma radiation reduced the handling and dis- 

 pensing problems as far as radiation exposure to personnel is concerned. 

 Tagging procedures were developed (Addendum C-l) to adsorb 1 Xe onto sand. 



Evaluation of 133 Xe -Tagged Sand 



Since sand tagged with a rare gas loses activity, due to diffusion as well 



133 / \ 



as to decay of the Xe (TqM = 5*27 d), data derived through use of 



Xe-tagged sand must be corrected to an "effective half -life." Test 

 samples prepared by the foregoing procedure were counted over a period of 

 several days and there was little incremental loss (over decay) (Fig. C-l) 

 Experiments also showed that no loss of activity could be attributed to 

 leaching by seawater (Table C-3)-In a test of labeling uniformity, random 

 quantities of tagged sand were counted and compared on the basis of the 



OFML-DWG 68-9547 























1 











\ 











\ 











\ 











N 



V 











V 



3 Xe- TAGGEC 



SAND 







> 



\ 



•- 



































~5 days 



\THtUHb 1 ILAL 



























X 











\ 











N 









N 



V 



200 300 



TIME.hr 



Fig. 



C-l. Apparent Half-Life 

 of 133 Xe-Tagged Sand 



quantity of sorbed Xe versus the 

 quantity of sand ( Table C-10-A1 though 

 the uniformity was fair, the radia- 

 tion counts from the samples varied 

 from high to low by a factor of 3. 



Subsequent tests have shown that spe- 

 cific minerals in sand do not tag with 

 the same efficiency. This causes the 

 individual sand grains to vary with 

 respect to the quantity of 13 Xe that 

 is adsorbed. 



Samples were also tagged, separated 

 into particle -size fractions, weighed, 

 and counted to determine whether those 

 fractions making up the bulk of the 



133 



sand contained the bulk of the Xe., 

 As shown in Fig.C-2,the correlation 

 between size distribution and xenon 

 sorption is good. The slight tailing 

 off of the large particles is prob- 

 ably due to specific minerals that 

 tend to concentrate in the large - 

 particle fractions. 



C-7 



